Optical communications techniques are being used increasingly in commercial communications applications. Moreover, the designers of optical communication systems continue to focus on techniques for increasing the transmission capacity of such systems. The current state of the art is such that per-channel data rates in the 10-20 gigabit per second (Gbit/s) range have been demonstrated.
The attainable data rates are limited principally by electrical signal processing considerations. In particular, electronic logic and other digital circuitry capable of operating at the highest rates that are attainable at any point in the evolution of the technology are typically not only expensive to design but are difficult to produce. Moreover, technology capable of providing the highest attainable speed is typically not sufficiently mature to guarantee reliable long-term operation.